This invention relates to weight measuring and value computing apparatus and more particularly to improved apparatus for weighing, computing a value and printing an article label showing the weight, price per unit weight and computed value of each of a plurality of successive articles. Apparatus is provided for indicating centering of the indicated zero within a fraction of the least significant indicated weight increment while the scale is empty.
In recent years the demand for increased efficiency has created the need for high speed measuring apparatus capable of automatically weighing successive articles and, for each weighed article, computing a value based upon a predetermined price per unit weight and printing an article label bearing such weight, price per unit weight and computed value. Such measuring apparatus is commonly used, for example, in supermarket meat departments. After a butcher cuts and divides meat into package portions, the meat may be automatically packaged and subsequently labeled by automatic weight measuring, value computing and label printing apparatus.
In the past, apparatus for weighing an article, computing an article price and printing an article label have included a combination of mechanical, optical and electrical elements. A typical prior art system of this type is described in U.S. Pat. No. 3,384,193 which issued on May 21, 1968 to William C. Susor et al and U.S. Pat. No. 3,453,422 which issued on July 1, 1969 to William C. Susor. This system includes a mechanical-optical scale which generates a digital signal corresponding to an article weight. A computer multiplies the measured weight by a price per unit weight, using a partial products method of multiplication, to obtain the article's value. The measured weight data, the price data and the computed value data are then supplied to a printer for producing an article label.
Although systems of this type have been extremely successful, there has been a need for faster-operating and more accurate systems. Entirely electronic scale systems using load cells for generating analog weight signals have been developed to meet these needs. The analog weight signal is digitized and the digitized weight is displayed on a digital indicator and supplied to a value computer. Electronic scale systems of this type must be manually checked and set to zero while no article is present on the scale platform. The zero setting must be checked and readjusted periodically because of long term drift caused, for example, by temperature changes and component ageing. However, prior art systems of this type have not permitted accurate determination and adjustment of the scale zero because the displayed weight is rounded off to the nearest digit. Even though the weight indicator displays a weight of zero, the scale system may be on the verge of changing to plus or minus one since there has been no means for centering the scale output within the zero increment.